I. Field of the Invention
The present invention relates generally to train positioning systems, particularly to systems for indexing a coupled string or trip of cars through a work station, one or more cars at a time during loading or unloading endeavors. More specifically, the present invention is directed to such a system which includes dog carriages having on-board drive systems to operate the carriages along a single tension chain. The system includes converging, diverging, separately-operated, horizontally extending cantilevered car engaging and propelling dogs designed to operate from one side against car bogey wheel frames.
II. Related Art
Trains, many containing 100 or more cars of identical or a variety of sizes, have long been acknowledged as desirable and efficient carriers of bulk raw materials such as coal, iron ore, limestone, various finely divided dry bulk agricultural products including grains, etc., and liquid or dry chemicals. These cars are typically filled from above and may be emptied using a rotary car dumper in the case of coal or iron ore. Liquid bulk cargo is typically unloaded by connecting outlets to large hoses with associated pumping equipment and opening bottom drain valves. The cargo then being pumped into tanks or tank trucks located near the tracks.
Cars shipping bulk agricultural products are bottom emptied into stationary freight handling equipment such as chutes, conveyor handlers or the like. These cars may be provided with a number of spaced bottom discharging hopper bins or chutes accessing the main storage volume of the car enclosed by sliding discharge gates. These are designed to be precisely positioned over dedicated recessed receiving facilities situated at fixed stations such as grain or coal bins and conveyors positioned beneath the railroad track.
In the bottom discharge operation, a connected train engine roughly positions one end of a string of cars to be unloaded close to the unloading facility. Because train engines are not well suited for indexing or precisely positioning individual cars or even sets of cars along the track, let alone precisely over individual bins, train positioning devices known as railroad car progressors or indexers have been built and operated at fixed stations.
Railroad car indexers of the class of interest include at least one car engaging and propelling member or “dog” for engaging at least one railroad car in a string or trip of cars and moving the string a given distance along the railroad track. The engaging members often situated and operated along an auxiliary indexer track or guideway juxtaposed in parallel relation to the railroad track in the fixed receiving facility. Fluid operated actuators such as hydraulic cylinders or chains and sprockets driven by hydraulic or electric motors supply power for moving the dog and pulling the railroad cars. U.S. Pat. No. 4,006,691, issued to Kacir et al, and U.S. Pat. No. 4,354,792, issued to Cornish, show train positioners that approach the train from alongside the track and including an engaging member arm which engages a car coupler from above.
It is known to provide a train positioning system having one or more carriages which include a pair of horizontally pivoting dogs mounted in opposed spaced relation and adapted to such that a first dog engages and moves a bogey frame in a first direction and a second dog engages and moves a bogey frame in the opposed direction. Such a system is illustrated and described in U.S. Pat. No. 6,267,059 to Brandt, a co-inventor in the present application.
It is also known to operate dog-carrying, train-positioning carriages using a reversing chain drive which includes an over/under or vertical sprocket drive system in which the gears and chain are at least partially enclosed to reduce exposure of the mechanism to the elements and the buildup of foreign materials. A system such as this is illustrated and described in U.S. Pat. No. 6,553,916 B2 to Goldbeck, a co-inventor in the present application.
While these prior systems have met with success, a need has also existed to simplify carriage drive systems that move the carriages and the system that operate the dogs. The present invention provides a dog carriage with an on-board drive system that requires only a single strand of tension drive chain. Separate, direct dog operation is also provided.